Display screen or a portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with a graphical user interface showing our new design; and,

FIG. 2 is a front view of a display screen or portion thereof with a graphical user interface in accordance to an alternate embodiment of our new design.

The outermost broken line perimeter showing the display screen or portion thereof and the broken lines showing elements of the graphical user interface are provided for the purpose of illustrating portions of the article and do not form part of the claimed design. 

CLAIM The ornamental design for a display screen or a portion thereof with a graphical user interface, as shown and described. 